It’s a cold day, you’ve turned your heating on and you sit back and relax, expecting the house to warm up like it usually does. This time things are a little different however, your radiators don’t quite seem to be getting warm, so you go over and feel around, it’s warm in patches, but cold in others.
You might be thinking the worst, that you need to call a plumber and get a whole new radiator, but don’t fear, this is a common problem and one you’re likely to come across every so often.
If you are desperate for a new radiator, check out our researched options for both oil filled radiators and electric radiators to keep you warm this winter.
In this guide, we’ll touch on how you can diagnose cold radiator issues, the common problems which cause it, and how to fix particular radiator issues. It’s quite a long post, so using the links below, you can find the answer to your particular query:
- How to Start Diagnosing Cold Radiator Issues
- Common Problems Causing a Cold Radiator
- How To Fix it When All My Radiators Are Cold
- How To Fix When The Whole Radiator Is Cold
- How To Fix Radiator Cold at Bottom or Top? (patchy)
- Why Are My Upstairs Radiators Colder Than Downstairs?
- How Do You Bleed Air From a Radiator at Home?
- How Do I Get Rid of Sludge in My Radiator?
- How To Prevent My Radiator From Getting Cold Again
Start Diagnosing Cold Radiator Issues
Like I’ve stated, it’s a common problem but to start understanding the issue, and knowing how to diagnose it properly is important.
The first and main question you have to ask yourself is, how many radiators are cold? A single radiator will indicate that it’s a problem with that radiator itself, however multiple or all radiators could indicate that there is an issue with other parts of the central heating system or even the boiler.
Why Would One Radiator Be Cold?
Have you found out that it’s just the one radiator? Then the issue is with the radiator itself, but that’s not quite the end of the diagnostic process. You need to find out where it is cold.
If the radiator is cold in parts, either at the top of the bottom, then the issue will be slightly different to if the whole radiator isn’t heating up.
For one that is cold in patches on the top of the bottom, it likely means that there are air pockets, which will mean you have to bleed the radiator, it may also be the case that if it’s cold on the bottom it’s a build-up of sludge that’s just sunk to the bottom. Both of these issues we will go through how to fix in the next sections.
When the whole radiator itself is cold it’s a little bit more complicated. What it could be is a limescale build-up in the pipe leading to the radiator itself, which is common if the radiator is very old, and you will, unfortunately, need to call a plumber. What you should check however is that the valves on both sides of the radiator are in fact on, it seems simple, but people often overlook it.
Why Are Multiple Radiators Not Getting Hot?
If none of your radiators is heating up, it’s likely an issue with your boiler which is the first thing that you should check. When your boiler is having an issue when the central heating is requested and the radiators aren’t heating up, it should indicate a fault code, this fault code will tell you the issue and recommended fix, I’ve written several guides on boiler fault codes, but it depends on the type of boiler you have as they all have different codes.
The only other thing that it could be is a blockage in your central heating system, you can try and locate the issue by following the pipe and see if it heats up in particular places, but if you’re not completely competent then you should call a professional.
Common Problems Causing a Cold Radiator
I’ve kind of touched on it in the section before, with a couple of the common causes based on your diagnostic results, but here’s a quick list of the overall most common radiator problems:
- Your radiator has air pockets and needs bleeding
- The boiler isn’t working or needs resetting
- The valves may be stuck in an off position
- Check that the water pressure is sufficient to push the water through the radiator system
- There could be an issue with the balance of the heating system
Fixing it When All My Radiators Are Cold
If all your radiators are cold then, unfortunately, it’s a larger issue than just your radiators. As previously stated this is likely an issue with your boiler or a blockage in your central heating system.
Here are the steps of things that you should do to try and fix the issue:
- Check to see if the boiler has a fault code
- If it does, find what the fault code means and what action you need to take
- Check that the gas supply to the house is working
- You should always try and reset your boiler if possible, this can clear a lot of issues
- It could be a low-pressure issue, make sure that your boiler is at the right pressure and if not repressurise it
If you’ve reset your boiler, checked your gas supply is working & the issue remains then, unfortunately, you are going to need to call a central heating engineer.
Fix For When The Whole Radiator Is Cold
Is the whole radiator cold? If you feel the radiator all over and every section of it is cold, here is what you should check step by step:
- Check the TRV (Thermostatic Radiator Valve) is on and the pins are moving properly by taking the head off
- If the TRV pins are stuck just give them a small tap and they should free up
- Check the other valve is open
- If it’s not yet fixed, turn off all the other radiators
- Does the “broken radiator” heat up? Then it’s an issue with one of the other radiators, so you can slowly start turning them on one by one
- Once you’ve located the radiator that is causing the problem, bleed it and turn it back on
- Still no luck? It’s likely a faulty or broken valve which you will need to look at getting replaced
How To Fix Radiator Cold at Bottom or Top? (patchy)
This is perhaps the most likely issue, a radiator that is either cold at the bottom or top which is often more patchy.
Here is what you need to do:
- Cold at the bottom: This is from a build up of sludge & you will need to do a powerflush of your system.
- Cold at the top of patchy: There’s air pockets in the radiator and you will need to bleed the radiator.
Why Are My Upstairs Radiators Colder Than Downstairs?
It might seem a bit of an odd one, your upstairs is roasting warm but downstairs freezing cold, or visa versa. There are two reasons for this, it could be that there is a lack of water in the feed or expansion cistern or it could be that there is a blockage in the ball valve.
There is only one main suggested fix and this is to you guessed it, bleed the radiator(s). It could however also be that the water pressure isn’t significant enough, so you should make sure your boiler is operating at optimum pressure.
How To Bleed Air From a Radiator at Home?
Most of the time, an issue with a radiator can be fixed simply by bleeding it or bleeding all the radiators around your home. Bleeding a radiator is pretty straight forward, and anyone can do it, simply follow these steps:
- First step is to turn off your central heating
- Then put a rag underneath the valve to catch any water
- Turn the radiator key anti-clockwise about a quarter turn which you should do until the air stops and the water runs smoothly
- Then turn the valve off
- Turn the system back on and your problem should be solved
How Do I Get Rid of Sludge in My Radiator?
To effectively remove sludge from your radiator, follow these steps:
- Turn Off the Heating System: Ensure the system is cool before proceeding.
- Bleed the Radiator: Open the bleed valve to release trapped air and water.
- Drain the Radiator: Open the drain valve to completely empty the radiator.
- Flush the Radiator: Connect a hose to the drain valve and flush the radiator with water to remove sludge.
- Refill the Radiator: Add water to the radiator using the filling loop.
- Bleed the Radiator Again: Release any trapped air after refilling.
- Check System Pressure: Ensure the system pressure is within the recommended range.
- Turn on the Heating System: Verify that the system is working correctly and check for leaks.
Preventing The Radiator From Getting Cold Again
Want to prevent this from happening? There are a couple of things that you can do to try and stop this happening regularly:
- Bleed your radiators – I do this yearly to try and prevent issues
- Run your radiators a few times during summer, just to clear out any sludge build up
- Get a powerflush, you may want to use a professional and it may cost a bit of money but it will clean your system
- Replace older Thermostatic Radiator Valves
- Regularly get your boiler services and keep up with maintenance